For transferring printed circuit base plates, it is already known to use a trolley having a loading table with reference dowels for receiving the plates to be printed, complete with suitable reference holes. In the known form of construction, the trolley, after receiving a plate to be printed, is moved from the loading zone to the printing zone where, with a considerable waste of adjustment, control and checking means, the trolley is located so that the base plate being printed is below the printing unit, in general a silk-screen printing device.
After the completion of the printing phase, the trolley returns to the loading unit where the printed plate is removed with known means from the reference dowels. A new base plate can then be loaded and forwarded to the printing zone.
The known trolley device is disadvantageous in that moving the trolley from the loading position to the printing position requires accurate positioning of the plate and wastes considerable mechanical and electrical energy. In addition, displacement of the entire trolley with the loaded plate below the printing unit does not permit high speed operation or high performance because to load a new plate it is necessary to first complete the entire printing operation, return the trolley to the initial position, and detach the printed plate from the plane provided with the reference dowels. A further disadvantage of the known trolly is its reduced accuracy relative to the positioning of the plate below the printing unit. This accuracy should approach hundredths of a millimeter. Moreover, the repeatability of positioning is not guaranteed with the conventional trolley.